Wiping cloth and the manufacture thereof



Dec. 9, 1958 IN V EN TOR. Mflfi/QA 6010/2440 BY WIPING CLOTH AND THEMANUFACTURE THEREOF Maurice A. Goldman, Wohurn, Mass, assignor to FibreProducts Laboratories, Inc., Newark, N. 5., a corporation of New JerseyApplication September 11, 1952, Serial No. 309,038

9 Claims. (Cl. 8-1156) This invention relates to wiping cloths and themanufacture thereof. It relates especially to wiping cloths for liquidhydrocarbons and the like, namely, a wiping cloth which may be used forWiping machinery or other parts whereby lubricating oil or the like maybe removed by absorption by the wiping cloth.

Wiping cloths for absorbing liquid mineral oils and other liquid.hydrocarbons are used in relatively large quantitiesfor wiping machineryof all kinds during the use thereof and during installation. The mostgenerally used wiping cloth for the purpose is a Woven textile fabrichaving. absorbent characteristics. Generally, the fabric used is afabric which was originally made and fabricated forv other purposes andwhich has been salvagedfo-r Wiping cloth usage. Such fabric as theresult of its use for other purposes generally accompanied by repeatedlaunderings is of a soft, porous and absorptivennature. For manypurposes, it is desirable that the wiping cloth be as lint free aspossible, and this fact imposes further limitations on the quality ofthe fabric employed. Generally, fabric suitable for wiping clothpurposes costs about 15 per 200 square inches of area. This is asubstantial cost item in view of the large quantities of wiping clothmaterial which are required about most plants using'machinery. In orderto minimize the. expense. incident to purchasing wiping cloth materialmany plants, after the wiping cloth material has been used untiltheamount of absorbed oil makes it no longer efiicient for its intendeduse, wash the. wiping cloth material using for the purpose a solvent forthe oil such as gasoline, naphtha, kerosene or the like. In largeindustrial plants the equipment for washing the wiping cloths usedtherein necessitates a substantial installation. Such equipment requiresmeans for washing the oil from the wiping cloths and since this is donewith gasoline or a similar solvent, it is normally desirable to alsoprovide means,

such as a distillation unit, for recovering the solvent. :The oil whichhas been removed from the used wiping cloths may also be recovered andused for certain purposes. On the average, the cost incident to theoperations involved in washing wiping cloths is about e per 200 squareinches of wiping cloth material.

Any wiping cloth for absorbing liquid mineral oils or the like isrequired to be substantially unaffected by such oils. Moreover, a.Wiping cloth should be resistant to solvents such as gasoline,-naphtha,kerosene or the like. Such resistance to solvents is necessary not onlyin case the wiping cloth is washed but also due to the fact that oilwiping cloths are frequently immersed in gasoline or kerosene, afteruse, and then wrung out in a partially cleaned condition for reuse.Further requirements of an oil-wiping cloth material are that it be ofsufiicient strength so that it will not tear under normal conditions ofuse and will not leave small pieces of the material on the machinery.The oil wiping cloth material also should be of such flexibility that itcan be caused to conform readily to the machinery parts so as tointimately coni atent ice tact the surfaces and absorb mineral oil orthe like therefrom. The necessity, in the case of most uses, of an oilwiping cloth being essentially lint free has been mentioned above.

It is an object of this invention to provide a fabric which as initiallymanufactured is designed for oil wiping cloth purposes. It is a furtherobject of this invention to provide a fabric suitable for use as awiping cloth for liquid mineral oils and the like which is highlyabsorptive of such mineral oils and which is unaffected by such mineraloils and by solvents for such mineral oils. It is a further object ofthis invention to provide a wiping cloth for the purposes stated which,while flexible and adapted to conform to the surfaces of the machineryparts, possesses adequate strength for wiping cloth usage. It is afurther object of this invention to provide an oil wiping cloth materialwhich is inherently lint free and can be used in connection with themost delicate machinery. It is an additional object of this invention toprovide an oil wiping cloth material having the aforesaid propertieswhich can be manufactured at a cost substantially less than thatincident to the purchase of the wiping cloth materials conventionallyused at the present time.

It is one of the features of this invention that an oil wiping cloth isafforded which comprises butadieneacrylonitrile copolymer resindistributed on and among cotton fibers comprised in an unspun sheet-likebody. It is a further feature of this invention that a substantialamount of the cutose coating ofthe natural cotton fibers is retained onthe cotton fibers in modified form-resulting from the action of an acidon the cutose coating, the modified cutose coating of the cotton fibersacting as a surface cement by which the 'butadiene-acrylonitrilecopolymer resin as disposed on and among the fibers is caused to firmlyadhere thereto.

During the initial growth of cotton fiber, the cell wall is first formedof pectose, waxes and primary cellulose. This is called the cutose orcuticle and contains up to 6% pectose which acts as a cement in thecellular fiber structure. As the fiber grows secondary cellulose isformed inside the cutose and the cutose remains as a coating on thecotton fiber. While in the mature fiber as a whole the percentage ofpectose is lower than during initial growth of the fiber, nevertheless,the amount of pectose in the cutose coating remains approximately thesame as that in the cutose during the initial growth of the cottonfiber. Usually, the amount of pectose in the cutose coating is in theneighborhood of about 6% thereof.

In the practice of this invention, the cotton fiber employed is onewhich has on the surface thereof either all or a substantial amount ofthe cutose coating of the natural cotton. Such cotton fiber in the graystate or substantially so is initially formed into a sheet wherein thecotton fibers are disposed in unspun relation. Ordinarily, this isaccomplished by a conventional carding operation and a sheet of cottonfibers which has been produced by carding the fibers while in the graystate is well suited for use according to this invention. However, thecotton fibers may be disposed in other ways in unspun relation as, forexample, after the fibers have been drawn to a greater or less extent.In a sheet of carded cotton fibers the fibers have some orientation inthe machine direction, but have substantial disposition in otherdirections. The extent of orientation of fibers can be increased by anoperation' such as drawing, and drawing to a more or less extent can beresorted to if strength characteristics in any particular direction aredesired. Moreover, sheets or webs of drawn unspun fibers can be plied ontop of each other with the fiber directions in the plies the same or atJ angle to each other as may be desired. The thickness of the unspunsheet that is employed may be any thickness which is sufficient topermit the sheet to be handled up to whatever weight of fabric isdesired for wiping cloth purposes. Ordinarily, the sheet of unspun graycotton fibers which is the most economical and also possesses superiorall-around utility for most purposes, is that which results from aconventional carding operation. By Way of example, in the manufacture ofa typical oil wiping cloth according to this invention a carded sheet ofgray cotton fibers may be used which is such that yards, about 36 inchesin width, weighs about 1 pound.

The butadiene-acrylonitrile copolymer is disposed on and among thefibers by coagulation of the resin in situ from an aqueous dispersionthereof. Also, the cutose coating of the cotton fibers is modified so asto act as a surface cement for the butadiene-acrylonitrile copolymerresin disposed on and among the fibers by subjecting the cutose coatingof the cotton to the action of a mineral acid. Since the mineral acidwhich modifies the cutose coating of the cotton fibers is also effectiveto coagulate the butadiene-acrylonitrile copolymer resin in the aqueousdispersion thereof the acid applied serves the double purpose ofeffecting the coagulation of the resin and modifying the cutose coatingfor the fibers so as to act as a surface cement for the coagulatedresin.

Aqueous dispersions of butadiene acrylonitrile copolymer resin used inthe manufacture of the wiping cloth of this invention are well known.Generally, such dispersions contain about 40% to 50% of thebutadiene-acrylonitrile copolymer, although other concentrations of thecopolymer may be used. Such dispersions have liquid characteristics,being similar in this regard to a latex which contains natural rubberinstead of the butadieneacrylonitrile copolymer. A number of differentconcerns produce aqueous dispersions of butadiene-acrylonitrilecopolymers. Such dispersions are sold by the Goodyear Tire & RubberCompany of Akron, Ohio, under the trademark Chemigum and that type whichis further identified as Latex Type 200, has been found to result in anespecially satisfactory product. Similar dispersions are produced by theB. F. Goodrich Company of Cleveland, Ohio under the trademark Hycar; andthe Hycar dispersion which is further identified as Type OR-25 has beenfound to possess very desirable characteristics for use according tothis invention. There are other similar dispersions ofbutadiene-acrylonitrile copolymers which are manufactured by otherconcerns.

The aqueous dispersion of butadiene-acrylonitrile copolymer may beapplied to the fibrous sheet-like body containing the gray cotton fibersin any suitable way. However, it is desirable that the dispersion bedistributed through the fibrous structure of the sheet so as to occur Inthe form of coatings for the individual fibers as distinguished fromforming a more or less continuous film on the surface of the sheetmaterial. It has been found that if the sheet material having thedispersion applied thereto is pressed between squeeze rolls whichsubject the sheet to light pressure, the dispersion becomes distributedon and among the fibers in preferred relation thereto. However, thedispersion may be applied to the sheet in any other suitable way so thatthe sheet will take up sufficient of the dispersion in order to providethe amount 01: butadiene-acrylonitrile copolymer desired in the finsheds eet.

After the aqueous dispersion of the butadiene-acrylonitrile copolymerhas been caused to impregnate the fibrous sheet comprising the unspungray cotton fibers the resultant sheet, while still wet with theimpregnated dispersion, has the solution of mineral acid applied theretoas to permeate the fibrous sheet and subject the cutose coating of thecotton fibers to the action of the acid. As above mentioned, the acid asso applied also serves to coagulate the butadiene-acrylonitrilecopolymer on and among the unspun fibers comprised in the sheet.

The acid treating step may be performed in any desired way. For example,the fibrous sheet after having been impregnated with the dispersion ofbutadiene-acrylonitrile copolymer may be contacted with a bathconsisting of an aqueous solution of the mineral acid. Alternatively,the mineral acid solution may be applied to the sheet which has beenimpregnated with butadiene-acrylonitrile copolymer dispersion bytransfer or by spray application. In any such case, it is desirable, asby passing the sheet over or between rolls, to cause the acid solutionto permeate the sheet so as to thoroughly contact the cutose coating ofthe cotton fibers. It is also preferable to subject the sheet to lightsqueezing so as to remove excess liquid.

After the acid treating step has been completed the sheet may beimmediately dried and then will be ready for use. Preferably, before thesheet is dried the sheet is subjected to a rinse with water so as towash out a substantial amount of the acid or acid salt used in the acidsolution and any other soluble by-products of the reaction. Normally,the concentration of the acid which is employed is such that even thoughthe fabric is not subjected to the rinsing step the retained acid andother by-products of the reaction do not detract from the utility of thefabric and do not result in degradation of the cotton fiber. However, ifthe acid used is at such a concentration as to cause gradual degradationof the fibers it may be desirable to subject them to the rinsing step.Moreover, by the use of a rinsing step the possibility of any adverseeffect either on the fiber comprised in the wiping cloth or on a surfacewhich may be subsequently wiped with the wiping cloth may be minimized.

The acid used in the acid treating step has a modifying effect on thecutose coating of the cotton fibers so as to provide a surface cement onthe fibers which greatly promotes the adhesion of thebutadiene-acrylonitrile copolymer to the fibers as disposed on and amongthe fibers as a result of coagulation in situ. This is believed to bedue to the fact that there is an interaction between the acid used inthe acid treating step and the insoluble pectose in the cutose coatingwhereby either directly or due to possible catalytic action all or asubstantial amount of the pectose becomes converted to soluble pectin.The cutose coating as thus modified by the conversion of the pectosetherein to pectin appears to have a special adhesive affinity for thebutadiene-acrylonitrile copolymer. The modified cutose coating remainsfirmly adherent to the body portion of the cotton fibers and in efiectaffords a priming coat of surface cement for causing thebutadiene-acrylonitrile copolymer as disposed on and among the cottonfibers to adhere strongly to the fibers. In any case regardless oftheory it has been found that if the foregoing steps are carried outusing cotton fibers which have been subjected to conventional chemicaltreatments for cleaning them so as to remove the normally unwantedcutose coating the resulting product is not suitable for use as an oilwiping cloth due principally to the fact that the material in such caseis lacking in sufiicient strength to permit such use thereof.

By the acid modification of the cutose coating of the cotton fibersaccording to this invention, the bond of the butadiene acrylonitrileresin with the fibers can be made such that upon increasing tensionimposed on the fabric to the point of rupture, the fibers themselvesbecome ruptured rather than merely pulling free Without breaking.

The action of the applied acid on the cutose coating of the cottonfibers appears to be promoted by mild heating. Thus, when the fabric isdried by passage over heated drying drums or is otherwise similarlyheated the fabric has substantially greater strength than if the fabricwas not warmed prior to completion of the drying. While the acid used inthe acid treating step serves to coagulate the butadiene-acrylonitrilecopolymer in the dispersion previously caused to impregnate the fabric,the acid solution applied reaches the cutose coating of the cottonasavis fibers with the result that the butadieneracrylonitrile copolymerbecomes deposited on and among the cotton fibers so that the copolymercontacts and adheres to the cutosecoating which has been modified by theaction of the acid in solubliz'ing at least a portion of the pectose inthe cutose coating.

Anystrong mineral acid or acid salt of a strong mineral acid may be usedin-the acid treating step. The mineral acids which are preferably usedare hydrochloric and sulfuric acids. However, nitric acid also may beused. Acid salts of strong mineral acids may also be used and the use ofsuch acid salts is preferable from the standpoint that such acid saltsusually can be more readily handled than the free mineral acids. Acidsalts which are especially desirable are ammonium sulfate, magnesiumsulfate, sodium bisulfate and alum. Whether a solution of a free mineralacid is used or a solution of an acid salt. is used the solution ineither case is .referred to herein and in t-he-claims as a solution of amineral acid for when an acid salt is used the acid salt becomes ionizedso that the resultant solution contains the ions which likewise arepresent when a free mineral acid is used.

In order to obtain the desired modification of the cutose coating of thefiber, the mineral acid, whether in thefree acid form or in the acidsalt form, should be a strong acid, i. e., one which becomes highlydissociated in aqueous solution. The acids and acid salts aboveexemplified are of this type and are to be contrasted with a relativelyweak acid such as phosphoric acid, trichloroacetic acid, acetic acid,and the like. The strong mineral acids effective for modifying thecutose coating of the cotton fibers have a dissociation constant greaterthan 2Xl0- When the mineral acid is used in the free acid condition theconcentration required to modify the cutose coating of the gray cottonfibers is somewhat greater than is the case when the mineral acid isemployed in the acid salt form. Thus, in the case of sulfuric acid ornitric acid, a concentration of at least about by weight is required inorder to obtain the desired modifying effect on the cutose coating. Toobtain a similar modifying effect a concentration of at least about 2.5%is required in the case of nitric acid. In the case of an acid salt suchas alum or Epsom salts (MgSO -7H O) all that is required is at leastabout 1% concentration.

In the interest of economy it is usually desirable to hold down theconcentration of the acid solution to a concentration only slightly inexcess of the minimum concentration for effecting the desiredmodification of the cutose, coating and the desired coagulation ofbutadiene-acrylonitrile copolymer on and among the fibers. However,greater concentrations may be employed. In the case of the acid saltsconcentrations up to the limit of solubility can be used without injuryto the fibers or deleterious effect other than the retention of an undueamount of salt and unnecessarily adding to the cost of the fabric. Inthe case of the free acid, if the concentration is too high there is thelikelihood of tendering the cotton fiber although the essential effectof the acid in coagulating the dispersion of the butadieneacrylonitrilecopolymer and in modifying the cutose coating would essentially be thesame as has been hereinabove described. Moreover, when the concentrationof free acid is relatively high the butadiene-acrylonitrile copolymertends to become coagulated in a more tacky condition than is the casewhen a more dilute solution is employed and such tackiness, ifexcessive, may result in rendering the sheet somewhat difficult tohandle during and immediately after the acid treating step. However, theeffect of relatively high concentration of acid in either of therespects above mentioned can be minimized'by the above mentioned rinsingstep which serves to remove excess acid from the fabric, thus minimizingthe possibility of tendering the cotton and reducing the tackiness ofthe butadiene-acrylonitrile copolymer as originally deposited on andamong the fibers. Moreover, if the butadiene-acrylonitrile copolymerresin which is caused to become coagulated on and among the fibers is ina condition of limited tackiness such that the sheet can bereadilyhandled, such initial tackiness of the coagulated copolymer disappearsas a result of the drying operation, preferably when the drying ispreceded by a rinsing step, with the result that the finished product isnon-tacky and has the feel of a soft charnois.

As a result of the above described operations thebutadiene-acrylonitrile copolymer resin becomes deposited on the cottonfibers in such a Way as to provide in the finished sheet a. high degreeof porosity and absorptiveness for oil. For most oil wiping clothpurposes the amount of resin solids which is coagulated on and among thecotton fibers is such that there are about 56 to 55 parts by weight ofthe resin solids per parts of fiber. This corresponds to approximately30% to 35 of the resin solids that is comprised in the finished wipingcloth. In order to afford sufficient body and strength the amount ofresin solids should be at least about 40 parts of the resin solids per100 parts by weight of the fiber. This corresponds to about 28% of theresin solids comprised in the finished wiping cloth. It usually is notdesirable to reduce the amount of resin solids in the oil wiping clothbelow about 25% by weight.

Notwithstanding the presence of such a substantial amount of resinsolids comprised in the finished wiping cloth, the wiping cloth has aremarkable capacity for absorbing oil. For example, a wiping clothwherein the resin solids constitute about 35% by weight thereof :is suchthat 100 grams thereof will absorb and retain without dripping up toabout 200 grams of oil. This high degree of absorptiveness for oildisplayed by the wiping cloth. of this invention may be compared withthat of conventional fabrics which have heretofore been used for oilwiping cloth purposes. Thus, the best grade, of wiping cloth previouslyused for the purpose is such that 100 grams thereof will not. absorbwithout dripping more than about grams of the same oil that was used intesting the absorptiveness of the oil wiping cloth fabric of thisinvention with the results hereinabove mentioned. It is thus seen thatan oil wiping cloth can be made according to this invention which issubstantally more effective for its intended purpose than the best gradeof conventional wiping cloths.

The absorptiveness of the wiping cloth of this invention for mineraloils and other similar materials appears to be only slightly affected bythe amount of the butadiene-acrylonitrile copolymer that is deposited onthe fibers. This was demonstrated by preparing an oil wiping clothfabric according to this invention containing about 30% .to 35 of theresin solids and then testing the fabric for oil absorptiveness as abovementioned. The fabric was then subjected to the operations ofimpregnation with a dispersion of the butadiene-acrylonitrile copolymerresin followed by the acid treating step so as to deposit an additionalamount of resin solids on the fibers for providing in the finishedfabric about 100 parts by weight of the resin solids for each 100 partsof the cotton fibers. While one might expect that the additional resinsolids would tend to fill up the interstices of the fabric and therebyimpair its absorptiveness this was not found to be the case, for thefabric was found to exhibit the same high degree of absorptivenessnotwithstanding the additional amount of resin solids contained therein.It is believed to be the case that even though the fibers as such arethoroughly coated with the butadiene-acrylonitrile resin, the resinbecomes deposited so that as carried on and among the surfaces of thecotton fibers the resulting fabric exhibits a high degree '7 ofabsorptiveness for mineral oil. In certain respects the finished fabricis in the nature of a sheet-like oil sponge which has a fiber matrix.

For most purposes it is not necessary that the finished fabric containmore than about 30% to 35% by weight of the resin solids, for amplestrength for most purposes in combination with a very high degree ofabsorptiveness can thereby be afforded. Upon increasing the proportionof resin solids contained in the finished product the strength of thefinished product can be increased as well as its resistance to abrasionand capacity to withstand long usage. Generally the amount of resinsolids does not exceed about 50% of the weight of the fabric. Expressedas a ratio, the ratio ofresin solids to fiber in the finished fabric isgenerally from about .4 to 1 to l to 1.

The finished fabric not only displays a high degree of absorptivenessfor oil as mentioned above but also exhibits in high degree thoseproperties which are desirable in an oil wiping cloth fabric. One ofthese properties is the very important one that the fabric is notadversely affected as the result of prolonged contact with mineral oilsabsorbed thereby or prolonged contact with solvents such as naphtha orgasoline. For example, the wiping cloth fabric of this invention hasbeen tested by immersing it in gasoline for 24 hours and then permittingthe gasoline to evaporate so as to restore the fabric to a drycondition. After such treatment no measurable change in dimensions wasfound to have occurred in any direction of the fabric. Moreover, thefabric retained all of its original properties as regards tensilestrength, as regards the feel of the fabric and as regards the capacityof the fabric to absorb oil. Such resistance to solvents is important inan oil wiping cloth fabric for, as above mentioned, wiping cloth fabricsare frequently kept immersed in a container of gasoline or kerosenesothat the wiping cloth fabric may, to some extent, be cleaned by suchimmersion and then wrung out for use in wiping machinery. Moreover, suchresistance to solvents is important if it should be desired to subjectthe wiping cloth fabric of this invention to any of the laundering"treatments conventionally used for cleaning ordinary oil wiping clothswhich employ a suitable solvent such as gasoline or kerosene.

While the wiping cloth fabric of this invention can be subjected tolaundering using a solvent such as gaso line or kerosene for thepurpose, the cost of the wiping cloth fabric of this invention is so lowthat the wiping cloths made therefrom can be thrown away after havingbeen used for wiping cloth purposes. As above mentioned the cost forlaundering conventional wiping cloth fabric is about 5 cents per 200square inches. The wiping cloth material of this invention is such thatit can be purchased for wiping cloth purposes at a corresponding cost,namely, about 5 cents per 200 square inches of the material. ing clothfabric of this invention is much more economical than conventionalfabrics used for wiping cloth purposes, for the initial cost is muchlower and the initial cost is so low that the wiping cloth can be thrownaway after use. Also there is no necessity for installing specialequipment for reconditioning used cloths.

Another advantage of this invention is that the oil wiping cloth isinherently such as to be lint free. The individual fibers of the unspungray cotton fiber fabric become coated with the butadiene-acrylonitrilecopolymer resin that is deposited on and among them, and there is nopossibility of the occurrence of lint. In connection with conventionalwiping cloth fabrics, those which are substantially lint free demandpremium prices and such freedom from lint can be afforded according tothis invention at a much lower cost.

For purpose of exemplification, a typical example of the practice ofthis invention will be described in connection with the accompanyingdrawing which shows sche- It is apparent, therefore, that thewipmatically and in side elevation one type of equipment which isadapted for producing the wiping cloth fabric of this invention on acontinuous basis.

For purposes of illustration the fabric employed may be a conventionalcarded cotton sheet about 36 inches wide and weighing about 1 pound for10 yards of the sheet. As above mentioned the carded cotton fibers arein the raw state and carry on the surface thereof the cutose coating ofthe natural fiber. This carded cotton sheet 1 is taken from the supplyroll 2 over guide rolls 3 and 4 to the nip between the squeeze rolls 5.An aqueous dispersion of butadiene-acrylonitrile copolymer resin such asthe aforesaid Chemigum Latex Type 200 which contains about 45% by weightof resin solids, i. e., butadieneacrylonitrile copolymerized in therelative proportion, by weight, of about 67% and about 33%,respectively, is applied to the rolls 5 throughout the length thereof asby the use of the pipes 6 to which the dispersion is supplied from asuitable source not shown and to which a series of nozzles is attachedthat distribute the dispersion on the surface of the rolls 5 uniformlyalong the length thereof. The dispersion is carried by the rotatingrolls to the nip between them where it is absorbed into the cardedcotton sheet 1. In order to facilitate the smooth laying of the cardedcotton sheet between the nip of the rolls 5 the sheet is preferablycontacted with one of the rolls slightly in advance of the nip as shown.Since the carded cotton sheet is absorptive the dispersion isimmediately absorbed into the sheet. The setting of the squeeze rolls 5is such that the weight of the aqueous dispersion retained by the sheetis slightly in excess of the weight of the cotton fiber. This willresult in the ultimate deposition on the cotton fibers of about 50 partsby weight of the resin solids per parts by weight of the cotton fiberson the dry basis. Any excess of the dispersion which is not retained bythe carded cotton sheet at the nip between the rolls 5 is permitted toHow laterally toward the ends of the rolls so that it may be collectedin the drip pan 7 and returned to the source of supply. In order tofacilitate the stripping of the impregnated carded cotton sheet from therolls 5 and in order to clear the drip pan 7 the impregnated sheet iscarried on the surface of one of the rolls as shown and is strippedtherefrom by the stripping roll 8.

By the foregoing operation the fabric is caused to be impregnatedthroughout with the dispersion of the butadiene-acrylonitrile copolymerand the dispersion is caused to become distributed in the form ofcoatings for the individual fibers so that the sheet is moistenedthroughout with the dispersion without substantial film formation at thesurfaces of the sheet.

After the sheet has been impregnated with the aqueous dispersion ofbutadiene-acrylonitrile copolymer it is immediately passed to the acidtreating step which can advantageously use equipment generally similarto that employed in connection with the initial impregnation step. Theimpregnated fabric may be passed between squeeze rolls 9 to the surfaceof which a solution of a mineral acid is applied as by uniform sprayingfrom the pipes 10. For example, the mineral acid solution employed maybe an alum solution of about 5% to about 10% concentration. Thissolution is applied to the impregnated fiber sheet so as to becomepermeated therethrough as by passing the sheet between the nip of thesqueeze rolls 9. The acid solution is thereby caused to come in contactwith the cutose coating of the fibers and serves to modify the cutosecoating while at the same time the butadiene-acrylonitrile copolymer iscaused to coagulate on and among the fibers. To facilitate the laying inof the impregnated sheet and the stripping of the acid treated sheet,the sheet is contacted with one of the rolls 9 substantially in advanceof the nip between these rolls and, after having been carried on thesurface of one of these rolls, is stripped therefrom using the strippingroll 11.

"Excessliquid is freeto flow downfrom'the ends of the 'rolls 9 soas tobe collected in'the drip pan '12.

If the fabric is to be rinsed with water this can be accomplished bypassing the impregnated and acid treated sheet between the squeeze rolls13 to which rinsing water is supplied by spraying from the pipes 14. Therinsing water is worked into the .sheet as the sheet is squeezed betweenthe .squeezerolls 13 .and the excess flows into the drip pan .15.Tofacilitatelaying in of the sheet the impregnated and. acidtreated.sheet is contacted with the rolls 13 in advance of the nip and iscarried on the surface of one of the rolls until stripped therefromusing the-stripping roll-16:

By the foregoing operations the chemical treatment of the sheet has beencompleted and it remains to dry the sheet. The treated sheet in the wetcondition may be carried to suitable drying equipment as by the use ofthe upper run of a continuous slat-type conveyor 17. The dryingequipment used may comprise a plurality of heated drying drums 18 whichmay be heated in any suitable way as by the use of hollow drums to theinterior of which steam is supplied. The drums 18 are preferablyenclosed in a compartment 19 through which heated air or other gaseousmedium can be circulated so as to carry out the moisture. As abovementioned the adhesion of the deposited coagulatedbutadiene-acrylonitrile copolymer to the fiber surfaces is promoted bythe action of the acid on the cutose coating of the cotton fibers. Suchaction continues during the drying of the fabric and is accelerated bythe heat of the drying drums. After the drying step the fabric may beremoved from the drying enclosure, as by passage over the rolls 20, 21and 22, after which it may be wound up into the roll 23. If desired thefabric can be slit into desired widths by suitable knives (not shown) soas to provide a plurality of rolls of desired width for oil wiping clothpurposes, suitable lengths merely being cut from the rolls. The oilwiping cloth fabric is in its finished condition ready for use as soonas the drying step has been completed.

While a specific form of equipment has been shown and described inconnection with the drawings it is apparent that any other suitableequipment may be used. For example, in the acid treating and rinsingsteps immersion in an acid bath and in a rinsing bath has been used inthe production of an oil Wiping cloth fabric according to thisinvention.

While the wiping cloth fabric of this invention is ordinarily made froma sheet consisting of unspun cotton fibers which carry on the surfacethereof at least a sub stantial amount of the cutose coating of thenatural fiber the principles of this invention would also be employed ifthe sheet material used were to contain a diluent material such as papermaking wood fibers so long as the cotton fibers carrying the cutosecoating are disposed in intimately contacting relation in order that inthe finished sheet the coagulated butadiene-acrylonitrile copolymer willbecome adherent to the acid modified cutose coating of the cotton fibersand bond them together. Ordinarily it is desirable that a fibrous sheetmaterial be used which consists at least in major proportion of cottonfibers carrying a substantial amount of the cutose coating of thenatural fibers.

I claim:

1. A method of making a fabric that is absorbent to liquid hydrocarbonscomprising the steps of impregnating a bibulous sheet of loose, unspun,natural cotton fibers carrying a substantial amount of the naturallyoccurring cutose coating, containing pectose, with abutadieneacrylonitrile synthetic rubber latex, applying to saidimpregnated sheet in the presence of said latex a strong mineral acidhaving a dissociation constant greater than about 2X10 capable ofconverting pectose in said cutose coating to pectin by reactiontherewith and capable of coagulating said latex in adherent relation tosaid cutose coating containing said pectin, the duration of 10 V contactwith said acid being snfiicient to obtain the aforesaid resultsand lessthan. that which resultsin substantial tendering of? said fibers,andhereafter drying the impregnated sheet.

2. Method of claim 1, wherein said sheet is rinsed with water priortothe drying step.

,3. A met'ho'd of making a fabric that is absorbent to liquidhydrocarbons 'being'thereby adapted for use as a wiping cloth whichcomprises the steps of impregnating a bibulous sheet' of loose, unspun,natural cotton fibers having thereon the cutose-coating of the naturalcotton fibers, containing pectose, with a butadiene-acrylonitrilesynthetic. rubber. latex, simultaneously reacting the peetose containedin said cutose coating with a strong mineral acid capable of convertingat least some of the pectose to pectin and capable of coagulating saidlatex on and among said fibers as a coating that overlays the re sultingpectin-containing cutose coating of said cotton fibers, applying to thesheet in the presence of said latex an aqueous solution of said strongmineral acid having a dissociation constant greater than 2 10- andblending with it said latex throughout said sheet, the duration ofcontact with said acid being sufficient to obtain the aforesaid resultsand less than that which results in substantial tendering of saidfibers, and thereafter heating and drying the impregnated sheet, theratio by weight to said fibers of said butadiene-acrylonitrile syntheticrubber being between about 0.4:1 and 1:1.

4. The method of claim 3 wherein said latex of butadiene-acrylonitrilesynthetic rubber is impregnated into said sheet by passing said sheetbetween a pair of rotating rolls in pressure contact with said sheet,said latex being applied to said sheet immediately in advance of the nipbetween said rolls.

5. A method of making a fabric that is absorbent to liquid hydrocarbonsbeing thereby adapted for use as a wiping cloth which comprises thesteps of impregnating a bibulous sheet of loose, upspun, natural cottonfibers having thereon the cutose coating of the natural cotton fibers,containing pectose, with a butadience-acrylonitrile synthetic rubberlatex by distributing the latex among the fibers as a coating uponindividual fibers and removing excess latex by pressing the sheetbetween rotating rolls in pressure contact with said sheet, therebyleaving the sheet in a moist, porous, absorptive condition, thenapplying to said sheet a solution of a strong mineral acid having adissociation constant greater than about 2 10- capable of convertingpectose in said cutose coating to pectin and capable of coagulating saidlatex, pressing the sheet between rotating rollers and therebysubjecting said cutose coated fibers to the action of said mineral acidand causing the synthetic rubber in the latex to be coagulated on andamong the fibers in contact with said cutose coating, the acidconcentration and the duration of its contact with said fibers beingsuch that said fibers are not substantially tendered by said acid, andthereafter drying the sheet while it is maintained at a superatmospherictemperature.

6. The method of claim 5 wherein said fiber sheet is impregnated withsaid latex by passing the sheet between squeeze rolls to which saidlatex is applied in advance of contact of the roll with the sheetwhereby said latex flows into said sheet, in advance of the nip betweensaid rolls and the sheet is carried on one of said rolls substantiallybeyond the nip therebetween prior to being stripped therefrom.

7. A Wiping cloth fabric which is absorbent to liquid hydrocarbons, andwhich comprises unspun fibers disposed in sheet form, a major proportionof said fibers being natural cotton fibers having adherent thereto in acoating, pectin derived from the naturally occurring cutose of saidcotton fibers, and coaguated, dried butadiene-acrylonitrile syntheticrubber distributed on and among said cotton fibers as a coating thereforin adherent relation to said pectin, said fibers being bonded togetherby said coating in porous absorptive relation in said fabric.

8. The fabric of claim 7 which contains at least about 25% by weight ofsaid butadiene-acrylonitrile synthetic rubber.

9. A fabric that is absorbent to liquid hydrocarbons comprising unspunfibers disposed in sheet form, a major proportion of said fibers beingnatural cotton fibers having adherent thereto in a coating, pectinderived from the naturally occurring cutose of said cotton fibers, andcoagulated, dried butadiene-acrylonitrile synthetic rubber distributedon and among vsaid cotton fibers as a coating therefor in adherentrelation to said pectin, said fibers being bonded together by saidcoating in porous, absorptive relation in said fabric, the ratio byweight of said butadience-acrylonitrile synthetic rubber to the fibersin said sheet being between about 0.4:1 and 1:1.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain Oct. 5, 1923 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No 2,863,715 December 9, 1958 Maurice A. Goldman It ishereby certified that error appears in the printed specification of theabove numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column 4, line 27, before 'fibers" insert n cotton column 10,

line 3 for "hereafter" read thereafter line 40, for "butadience readbutadiene- Signed and sealed this 9th day of June 1959,

SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner ofPatents

1. A METHOD OF MAKING A FABRIC THAT IS ABSORBENT TO LIQUID HYDROCARBONSCOMPRISING THE STEPS OF IMPREGNATING A BIBULOUS SHEET OF LOOSE, UNSPUN,NATURAL COTTON FIBERS CARRYING A SUBSTANTIAL AMOUNT OF THE NATURALLYOCCURRING CUTOSE COATING, CONTAINING PECTOSE, WITH ABUTADIENEACRYLONITRILE SYNTHETIC RUBBER LATEX, APPLYING TO SAIDIMPREGNATED SHEET IN THE PRESENCE OF SAID LATEX A STRONG MINERAL ACIDHAVING A DISSOCIATION CONSTANT GREATER THAN ABOUT 2X10-**1 CAPABLE OFCONVERTING PECTOSE IN SAID CUTOSE COATING TO PECTIN BY REACTIONTHEREWITH AND CAPABLE OF COAGULATING SAID LATEX IN ADHERENT RELATION TOSAID CUTOSE COATING CONTAINING SAID PRECTIN, THE DURATION OF CONTACTWITH SAID ACID BEING SUFFICIENT TO OBTAIN THE AFORESAID RESULTS AND LESSTHAN THAT WHICH RESULTS IN SUBSTANTIAL TENDERING OF SAID FIBERS, ANDHEREAFTER DRYING THE IMPREGNATED SHEET.
 7. A WIPING CLOTH FABRIC WHICHIS ABSORBENT TO LIQUID HYDROCARBONS, AND WHICH COMPRISES UNSPUN FIBERSDISPOSED IN SHEET FORM, A MAJOR PROPORTION OF SAID FIBERS BEING NATURALCOTTON FIBERS HAVING ADHERENT THERETO IN A COATING, PECTIN DERIVED FROMTHE NATURALLY OCCURRING CUTOSE OF SAID COTTON FIBERS, AND COAGUATED,DRIED BUTADIENE-ACRYLONITRILE SYNTHETIC RUBBER DISTRIBUTED ON AND AMONGSAID COTTON FIBERS AS A COATING THEREFOR IN ADHERENT RELATION TO SAIDPECTIN, SAID FIBERS BEING BONDED TOGETHER BY SAID COATING IN POROUSABSORPTIVE RELATION IN SAID FABRIC.